Conventionally, as the above radio communication method and the radio communication device, there are ones, for example, disclosed in JP-A-2003-229869. FIG. 17 shows the radio communication method described in the JP-A-2003-229869, which shows a radio communication method in which radio communication devices directly make communication with each other without disposing a control station in a radio network.
In FIG. 17, a radio communication device 1702 sets a notification cycle of management information at a predetermined time interval and transmits management information in which reception timing information indicating a start position for receiving information on the radio communication device 1702, reception window information, and reception cycle information are written (T1). Another radio communication device 1701 which was able to receive the management information stores the reception timing, the reception window and the reception cycle, associating them with the communication device number of the radio communication device 1702. Then, when the radio communication device 1701 transmits information, it determines the reception start position in the corresponding radio communication device 1702 based on the reception timing, the reception window and the reception cycle of the correspondent node, and transmits the information at the timing of the reception start position.
The management information is exchanged between all radio communication devices in a management information exchange area by transmitting beacons.
However, by the movement of the radio network to which the radio communication device belongs, a beacon in the management information exchange area sometimes collides with a beacon transmitted from a radio communication device in another radio network.
As a countermeasure for this collision, there is a radio communication method described in JP-A-2004-40645. In the radio network according to the radio communication method, the radio communication devices do not respectively communicate with each other, but rather a coordinator which is a control station is disposed which transmits beacons of the radio network to which the station belongs. FIG. 18 is a conceptual diagram showing the radio communication method.
In FIG. 18, when plural radio networks (which correspond to “piconet”s in the drawing) collide with each another on the same frequency channel, the control station of one radio network temporarily sets a buffer super frame cycle 1801 to keep coexistence of the radio networks. When devices other than the control station receive a beacon signal of the buffer super frame cycle 1801, they temporarily set a short super frame cycle based on the super frame cycle to perform fine adjustment of the timing of transmitting the next beacon. A device which could not receive the beacon searches for a beacon of the radio network to which the device belongs during redundant time, and searches for the start timing of a new super frame cycle. The radio communication device can shift the transmission timing of beacons when the beacon collides with the beacon of another radio network by using the buffer super frame cycle 1801.
The above method can be utilized in the case where the radio communication device which transmits beacons in one radio network is the control station only, but when radio communication devices in the respective radio networks transmit beacons as shown in the JP-A-2003-229869, there are a problem that it is difficult for radio communication devices to shift transmission periods of beacons all at once.